A Critic Takes On the Logic of Female Orgasm

By DINITIA SMITH

Published: May 17, 2005

Evolutionary scientists have never had difficulty explaining the male orgasm, closely tied as it is to reproduction.

But the Darwinian logic behind the female orgasm has remained elusive. Women can have sexual intercourse and even become pregnant -- doing their part for the perpetuation of the species -- without experiencing orgasm. So what is its evolutionary purpose?

Over the last four decades, scientists have come up with a variety of theories, arguing, for example, that orgasm encourages women to have sex and, therefore, reproduce or that it leads women to favor stronger and healthier men, maximizing their offspring's chances of survival.

But in a new book, Dr. Elisabeth A. Lloyd, a philosopher of science and professor of biology at Indiana University, takes on 20 leading theories and finds them wanting. The female orgasm, she argues in the book, ''The Case of the Female Orgasm: Bias in the Science of Evolution,'' has no evolutionary function at all.

Rather, Dr. Lloyd says the most convincing theory is one put forward in 1979 by Dr. Donald Symons, an anthropologist.

That theory holds that female orgasms are simply artifacts -- a byproduct of the parallel development of male and female embryos in the first eight or nine weeks of life.

In that early period, the nerve and tissue pathways are laid down for various reflexes, including the orgasm, Dr. Lloyd said. As development progresses, male hormones saturate the embryo, and sexuality is defined.

In boys, the penis develops, along with the potential to have orgasms and ejaculate, while ''females get the nerve pathways for orgasm by initially having the same body plan.''

Nipples in men are similarly vestigial, Dr. Lloyd pointed out.

While nipples in woman serve a purpose, male nipples appear to be simply left over from the initial stage of embryonic development.

The female orgasm, she said, ''is for fun.''

Dr. Lloyd said scientists had insisted on finding an evolutionary function for female orgasm in humans either because they were invested in believing that women's sexuality must exactly parallel that of men or because they were convinced that all traits had to be ''adaptations,'' that is, serve an evolutionary function.

Theories of female orgasm are significant, she added, because ''men's expectations about women's normal sexuality, about how women should perform, are built around these notions.''

''And men are the ones who reflect back immediately to the woman whether or not she is adequate sexually,'' Dr. Lloyd continued.

Central to her thesis is the fact that women do not routinely have orgasms during sexual intercourse.

She analyzed 32 studies, conducted over 74 years, of the frequency of female orgasm during intercourse.

When intercourse was ''unassisted,'' that is not accompanied by stimulation of the clitoris, just a quarter of the women studied experienced orgasms often or very often during intercourse, she found.

Five to 10 percent never had orgasms. Yet many of the women became pregnant.

Dr. Lloyd's figures are lower than those of Dr. Alfred A. Kinsey, who in his 1953 book ''Sexual Behavior in the Human Female'' found that 39 to 47 percent of women reported that they always, or almost always, had orgasm during intercourse.

Dr. Lloyd said there was no doubt in her mind that the clitoris was an evolutionary adaptation, selected to create excitement, leading to sexual intercourse and then reproduction.

But, ''without a link to fertility or reproduction,'' Dr. Lloyd said, ''orgasm cannot be an adaptation.''

Not everyone agrees. For example, Dr. John Alcock, a professor of biology at Arizona State University, criticized an earlier version of Dr. Lloyd's thesis, discussed in in a 1987 article by Stephen Jay Gould in the magazine Natural History.

In a phone interview, Dr. Alcock said that he had not read her new book, but that he still maintained the hypothesis that the fact that ''orgasm doesn't occur every time a woman has intercourse is not evidence that it's not adaptive.''

''I'm flabbergasted by the notion that orgasm has to happen every time to be adaptive,'' he added.

Dr. Alcock theorized that a woman might use orgasm ''as an unconscious way to evaluate the quality of the male,'' his genetic fitness and, thus, how suitable he would be as a father for her offspring.

''Under those circumstances, you wouldn't expect her to have it every time,'' Dr. Alcock said.

Among the theories that Dr. Lloyd addresses in her book is one proposed in 1993, by Dr. R. Robin Baker and Dr. Mark A. Bellis, at Manchester University in England. In two papers published in the journal Animal Behaviour, they argued that female orgasm was a way of manipulating the retention of sperm by creating suction in the uterus. When a woman has an orgasm from one minute before the man ejaculates to 45 minutes after, she retains more sperm, they said.

Furthermore, they asserted, when a woman has intercourse with a man other than her regular sexual partner, she is more likely to have an orgasm in that prime time span and thus retain more sperm, presumably making conception more likely. They postulated that women seek other partners in an effort to obtain better genes for their offspring.

Dr. Lloyd said the Baker-Bellis argument was ''fatally flawed because their sample size is too small.''

''In one table,'' she said, ''73 percent of the data is based on the experience of one person.''